1. Field
A linear compressor is disclosed herein.
2. Background
In general, compressors are machines that receive power from a power generation device, such as an electric motor or a turbine, to compress air, a refrigerant, or various working gases, thereby increasing a pressure thereof. Compressors are being widely used in home appliances or industrial fields.
Compressors may be largely classified into three different types. The first type is a reciprocating compressor, in which a compression space, into and/from which a working gas, such as a refrigerant, is suctioned and discharged, is defined between a piston and a cylinder to allow the piston to linearly reciprocate within the cylinder, thereby compressing the refrigerant. The second type is a rotary compressor, in which a compression space, into and/from which a working gas, such as a refrigerant, is suctioned or discharged, is defined between a roller that eccentrically rotates and a cylinder to allow the roller to eccentrically rotate along an inner wall of the cylinder, thereby compressing the refrigerant. The third type is a scroll compressor, in which a compression space into and/from which a working gas, such as a refrigerant, is suctioned or discharged, is defined between an orbiting scroll and a fixed scroll to compress the refrigerant while the orbiting scroll rotates along the fixed scroll.
A linear compressor is being widely developed which has a simple structure and which is directly connected to a drive motor, in which a piston linearly reciprocates, to improve compression efficiency without mechanical losses due to motion conversion. In general, the linear compressor suctions and compresses a refrigerant within a sealed shell while the piston linearly reciprocates within the cylinder by a linear motor and then discharges the compressed refrigerant.
The linear motor includes a permanent magnet provided between an inner stator and an outer stator. The permanent magnet is driven to linearly reciprocate by electromagnetic force between the permanent magnet and the inner (or outer) stator.
As the permanent magnet is connected to the piston, the refrigerant is suctioned and compressed while the piston linearly reciprocates within the cylinder and then the compressed refrigerant is discharged. A linear compressor is disclosed in related art Korean Patent Publication No. 2016-0024217, which is hereby is incorporated by reference, having a feature in which a coupling part protrudes from an outer circumferential surface of a flange of a cylinder, and a groove for seating the flange of the cylinder and the coupling part is defined in a top surface of a frame. Also, the cylinder is fixed to the frame through a coupling member, such as a bolt, passing through the coupling part.
As described above, in a case of the linear compressor in which the cylinder is coupled to the frame through the bolt, bolt coupling is performed at a plurality of points. Thus, if bolt coupling forces at the points are not completely the same, it is difficult to carry out a centering operation for aligning a center of the cylinder and a center of the frame.
When the center of the cylinder and the center of the frame do not match each other, it is difficult to form a gas passage through which a refrigerant gas for lubricating flows. That is, if the centering or alignment is not accurately performed, an outer circumferential surface of the cylinder and an inner circumferential surface of the frame may come into contact with each other, resulting in passage resistance because the gas passage is closed.
In addition, it is difficult to form the coupling part on the outer circumferential surface of the cylinder and form the groove for seating the coupling part in a top surface of the frame. Processing costs are also high.
A process for coupling equipment and parts is additionally required while the bolt is coupled, and thus, manufacturing costs increase. Also, a coupling force of the coupling member may be loosened due to vibration generated during driving of the compressor. As a result, vibration and noise may further increase, and the compressor may be deteriorated in reliability.
In order to solve the above-described limitations, a method of inserting and fixing the cylinder into an insertion hole in a press-fitting manner may be applied. However, in a case of the press-fitting manner, the cylinder may be deformed in shape by a high pressing force generated on the press-fitting surfaces of the cylinder and the frame. That is, an inner diameter of the cylinder may be deformed by the pressing force, and thus, the piston may not be properly inserted into the cylinder. Also, although the piston is inserted into the cylinder, the reciprocating motion of the piston may not be performed smoothly.
As vibration generated while the piston reciprocates is directly transmitted from the cylinder to the frame, when the piston reciprocates at a high frequency of 90 Hz or more, the vibration of the compressor may excessively increase. Also, when the outer circumferential surface of the cylinder is press-fitted into the frame, there may be no space between the cylinder and the frame. Thus, the cylinder may expand due to heat generated while a refrigerant is compressed at a high-temperature and high-pressure damaging the frame.